Unlikely there would have been a Wilhelm
If Victoria II has ascended the throne, it is unlikely she would have been wed to the German Crown Prince.
Edit: I checked the timeline and as I suspected Victoria II married Fredrick long before the death of Victoria I. So, there could have been a Wilhelm. Still, I am not an expert on royal succession, but it would be very odd to wed 2 crown royals without a plan to merge the kingdoms.
Alternate history is never easy :)